Integrated knowledge of the development and function of the nervous system can be gained by the study of the underlying genetic control because it is the genes that specify the development of structures that generate functions. In Drosophila, it is possible to induce single gene mutations that alter processes in the development or function of the nervous system. The proposed studies are directed at establishing the Drosophila ventral ganglion as a suitable system to analyze the physiological defects in neurological mutants and to examine how the neuronal development is affected by the mutations. We will use intracellular staining and transynaptic axonal transport techniques to identify motorneurons in the ventral ganglion and to observe its development in normal and mutant animals. The development of membrane electrical properties in both normal and mutant animals will be investigated by intracellular measurements. We will analyze the mechanisms for altered nerve excitabilities in various mutants and the timing of the expression of the mutant phenotypes. Since it is possible to obtain recordings from the soma, axon and nerve terminus of the motorneurons, we will look for any possible differences in membrane electrical properties in these cell regions as indicated by differential effects of mutations, drug agents, and ionic environment. The use of our temperature-sensitive mutant, in which axonal conduction fails at high temperature, will provide a unique opportunity to study the effect of blocking action potentials on neuronal development.